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IMAGES: Neither Animal Nor Vegetable

Yellow or green in daylight, uranium-containing autunite crystals fluoresce under an ultraviolet lamp, making the mineral a favorite of collectors. At this online atlas from geologist J. Theo Kloprogge of Queensland University of Technology in Brisbane, Australia, you can dig up a wealth of physical and chemical data about autunite and more than 3600 other minerals. The database lists 13 standard properties for each mineral, including hardness, specific gravity, and tenacity, or resistance to breaking. Many entries furnish photos, and Kloprogge is adding Raman and other spectra, which are useful for identifying samples and analyzing their structure.